Studies have indicated that in the selection of cooking appliances, consumers value three factors of relatively equal importance: aesthetics, cleanability and performance. The popular electric smoothtop ranges, i.e. those having a cooktop surface that is flat and uninterrupted, score well in all three factors. They have been available for several years now. With their smooth uninterrupted cooktops, such electric smoothtops satisfy consumer aesthetics by giving these appliances their sleek, modern appearances. Cleanability needs are met by these smooth electric tops in which the cooking areas have no apertures and/or surface irregularities. Without apertures or irregularities, spilled matter and/or other debris can not collect within these types of rangetops.
For years, chefs and other cooking experts have preferred the performance of gas over electric cooking. However, because no gas surface rangetops have adequately addressed aesthetic and cleanability, the general consumer market has tended away from gas rangetops. There has been a gradual decline in gas cooking appliance sales despite their performance advantage.
Gas surface rangetops typically incorporate a cooking vessel support or grate on which a cooking pot or pan rests over a gas burner projected through an opening in such rangetops. These gas burners are loosely or rigidly secured to a chassis of the appliance. In most modern applications, burners are typically fixedly or loosely secured to the cooktop with a burner seal arrangement that enhances cleanability. Such gas burner arrangements are similar to those of conventional (i.e. non-smoothtop) electric cooking ranges where an open heating element protrudes through an aperture in the cooktop surface for both heating and supporting the cooking pot or pan.
In the past few decades, there have been several different attempts to duplicate an electric smoothtop with gas equivalents. They include using: 1) a gas burner under the cooktop surface, i.e. a gas smoothtop; 2) a gas burner assembly that passes through an aperture in a planar cooktop surface with a separate grate above; 3) a gas burner that passes through an aperture with an integral grate in the cooktop surface; 4) a full or partial burner assembly that is integral with the cooktop surface, the grate being: (a) part of the cooktop surface; (b) a non-integral portion of the burner or (c) a separate component; and 5) an aperture in the cooktop surface for a full or partial burner assembly with the grate and/or burner being a part of that cooktop surface.
Perl U.S. Pat. Nos. 3,870,457 and 3,968,785 disclosed a gas smoothtop range or cooktop having a powder blue flame rather than a radiant type burner beneath their glass ceramic top. Herbert U.S. Pat. No. 5,295,476 disclosed a radiant burner below the cooktop plate to enable a gas radiant smoothtop that might compete more effectively with conventional open flame burners.
Schott Glas developed a ‘gas-under-glass’ smoothtop that intended to address the cooking application, control and venting issues with radiant burner heating. That arrangement offered no distinct advantage compared to electric smoothtops, however. Such configurations actually raised the price of gas smoothtops significantly as compared to electric smoothtops due to: (i) the complexity of combustion venting; and (ii) the need for additional safety controls. Also, with a gas burner under a smoothtop surface, the cooking performance advantage of being able to visually identify heat output and make rapid adjustments thereto was lost.
Bennett et al U.S. Pat. No. 5,046,477 disclosed a glass cooktop having a burner opening with an arrangement for supporting the gas burner independent of the cooktop. The cooktop apparatus of Taplan et al U.S. Pat. No. 6,032,662 included a cooktop panel of glass ceramic, glass or ceramic in a structural housing. That cooktop panel had a cutout for accommodating a gas burner held by an assembly with a collar that annularly overlapped a portion of panel at the cutout. The aforesaid collar had an inner edge which defined a first abutment for gas burner engagement. A resilient metal element attached to that burner and extended outwardly therefrom for engaging with a lower side of the panel. That lower side defined a second abutment against which the metal element applied force to hold the burner on the panel via the collar and resilient element. A seal clamp between the collar and panel prevented spillage from reaching the structural housing through the cutout.
Taplan et al U.S. Pat. No. 6,170,479 disclosed attaching an atmospheric gas burner to an opening in a glass or glass-ceramic cooking surface for reducing assembly time, the number of components required and easier cleaning of an assembled unit. Arntz et al U.S. Pat. No. 6,173,708 disclosed a gas burner mounting assembly with an injector whose main body portion was positioned between a chassis member of the appliance and a ceramic based cooktop. That injector was mechanically secured to the cooktop for allowing its gas injector to flex with that cooktop.
Taplan U.S. Pat. No. 6,209,534 disclosed a glass-ceramic, molded cooktop plate with a covered, upwardly projecting portion that formed a gas/air mixing chamber for a burner. Between the cover and projecting portion, burner ports were provided to burn a gas/air mixture. Miller U.S. Pat. No. 6,148,811 showed a combined burner and grate structure integral with its cooktop surface.
With any cooktop made from glass, breakage can occur during its manufacture. Defects start as micro-cracks, which lead to stress risers unavoidable in the normal processes for drilling an aperture in such products. Breakage can also occur during usage, especially with a grate located near or on the burner proper. Impact with the burner/grate causes a high bending moment for such cooktops. With cooktops made from thermally- or chemically-tempered soda lime glass, thermal shock from high temperatures proximate the burner can also cause breakage. For the latter glass, a maximum temperature limit must be observed to retain its temper and mechanical—thermal loads.
Braccini U.S. Pat. No. 6,257,228 addressed micro-crack breakage and cleanability by creating a molded, raised part above the surface. That part prevented liquid food from falling through and reaching the burner proper. However, additional thermal processing raised the cost of such cooktops, and holes still have to be drilled therethrough.
Other solutions for preventing the glass from overheating and breaking use large diameter borings and place a sheet metal pan underneath. The edge of each boring sits in a collar. With that practice, aesthetics is lost and cleaning these large borings becomes an issue.
Gabelmann U.S. Pat. No. 6,505,621 addressed thermal breakage for a cooktop having at least one gas burner cutout by applying a reflective coating to the upper side of his cooktop plate. While reducing the thermal load to the plate, it added manufacturing costs.
Both gas and electric cooktops suffer from the disadvantage of requiring a dedicated burner/heating position for cooking. And while burners of different power or heating characteristics are available, they are still relatively fixed in number, variety and location on a given cooktop. This limits the user in choice of cooking style or function. Electric smoothtops have tried to partially address this problem with “bridge burners”, i.e., two non-concentric circular burners morphed into an oblong or ovular burner ring useful for griddles, long fish pans and the like. Such a combination has been disclosed for gas cooktops in Yam et al Published U.S. Application No. 2005/0142511. These gas burners tend to heat individual segments unevenly when the bridge is deactivated, however.
To compensate for dedicated heating positions, commercially available gas rangetops (as well as electric) such as that disclosed in Berlik U.S. Pat. No. 4,457,293 have modular burner cartridges, otherwise known in the art as “modular cooking units”, “surface burner units”, “drop-in” or “plug-in” cartridges. Such rangetops have recessed burner boxes or burner pans otherwise known in the art as “compartments” in the rangetop's top surface (cooktop surface). These units or cartridges are dropped into a compartment to form an arrangement similar to conventional gas surface rangetop. For example, one rangetop may include a gas burner cartridge for a first compartment and a grilling cartridge for a second compartment.
While permitting a change in burner types, these cartridges still require a complete “unit”, i.e., cooktop surface, burner, and housing in which all components are fastened together. As such, these cartridges tend to be bulky and therefore cumbersome to switch between. In addition, the burner cartridge system also offers no significant burner performance especially when compared to a dedicated, fixed-position gas-burner rangetop. This is partially due to the cartridge/rangetop configuration, which places more overall constraints on the gas circuit's performance.
Beach et al U.S. Pat. No. 4,705,019 disclosed a range with selectively interchangeable burners. The latter burners were lighter in weight as they did not require a complete “unit”. Instead, these burners were installed in the compartment (burner box). Such compartments would be difficult to clean as the compartment bottom is significantly below the cooktop surface. The compartments are below countertop level, relatively deep, and permanently fixed in place. Switching between surface burner cartridges could also be quite cumbersome for similar reasons. Regardless, the burner well area, i.e. that portion of the burner cartridge, or the bottom of the burner pan into which the modular burner cartridges drop, precludes its use as a food preparation or work area.
Modularity is a good marketing strategy and a useful concept. It addresses the fundamental need that various cooking styles require different burners. Modularity frees the user from the limitations of a fixed-position rangetop while allowing one to add (or change) burners to match the cooking functions needed. Modularity is also beneficial during the initial purchase. It allows consumers to buy only what they need with the option of adding more burners later to meet changing needs or preferences.
For any smoothtop (electric or gas) made from a brittle plate, damage to the flat cooking surface can result by the mere dropping of a cook pan. Such damage may require replacing the whole cooking surface. The ability to change cooktop surfaces in case of breakage, while adding greater modularity with changing smoothtop colors and/or design motifs would be desirable. It would also supply an advantage not present with current cooktops having glass-ceramic top surfaces.
Hence, there remains a need for gas cooktops that: (a) provide the performance characteristics of conventional gas cooking; (b) improve modularity; (c) rival the cleanability and aesthetics of an electric smoothtop without having the burner hardware mounting issues at the manufacturing level; and (d) permits using the area in the vicinity of the burner head, when not used for cooking, as a work surface area without burner hardware obstructions.